1. Field of the Invention
The present invention relates generally to the field of orthodontics and, more particularly, to cemented-types of palate expander apparatus and related expander screws used for widening the palate of dental patients, especially, young dental patients.
2. Background Discussion
Orthodontia procedures are commonly used for widening, that is, expanding, excessively narrow palates (upper jaws) of dental patients, especially young patients, whose palates still retain some plasticity or malleability. The understanding of the present inventor is, for example, that such palate expansion procedures--which are performed to permit patients to breathe more easily and/or to improve dental malocclusions and/or facial appearance--are performed in the United States at a rate of approximately five hundred per day or about one hundred twenty-five thousand per year.
The orthodontia procedure of palate expansion (i.e., the widening of the upper jaw) of individuals appears to have been first described in about 1860 by E. C. Angell. As historically described, the Angell dental appliance included a jackscrew assembly (now referred to as an expansion screw assembly) having joined thereto a pair of palate-engaging "collars." In use, the appliance was wedged in place in the roof of a patient's mouth with the collars bearing against the patient's opposing bicuspid teeth. The jackscrew of the appliance was described as then being actuated by a "notched dime" in a manner causing the attached collars to be moved apart so as to exert a sidewardly-directed force on the teeth against which the collars pressed. To achieve palate widening, the jackscrew was actuated in small increments of rotation over a period of several weeks such that the wearer's palate was gradually widened by a total of about four to seven millimeters without undue patient discomfort. After the desired palate expansion was attained and stabilized, the jackscrew was re-rotated to loosen the appliance enough so that it could be removed from the patient's palate.
It is significant to note that most orthodontic palate expanders presently used in the dental profession are modeled after the Angell palate expander. In this respect, many modern palate expander apparatus comprise a jackscrew assembly (which is an off-the-shelf item procured from dental supply companies) to which custom-fitted palate blocks or pads are connected through left-hand and right-hand threaded plates which form part of the jackscrew assembly. Other modern types of palate expanders are constructed with a metal framework joined to the jackscrew assembly and terminating in tooth bands soldered to the framework. Expansion of the jackscrew moves opposite side portions of the framework apart and exert palate-widening pressure on the palate through the tooth bands. In still other versions, the metal framework joined to the jackscrew assembly is configured such that no tooth bands are used.
The particular type of palate expander apparatus used by an orthodontist depends upon such factors as the shape of the patient's palate, the amount of palate expansion to be achieved and upon the orthodontists experience and preference. However, all of these versions of palate expanders use the same basic type of jackscrew expansion screw which is operated in a common manner.
One improvement to the Angell palate expander appliances that instead of operating the jackscrew by a "notched dime" (as described by Angell) modern palate expanders utilize a stiff, key-shaped stainless steel wire or pin, called an activation key. In operation, this key is inserted into a hole formed through central regions of the jackscrew and turns the jackscrew in windlass fashion. Because of clearance restrictions--both of the expansion screw assembly and the patient's palate after installation of the apparatus--the arcuate travel of the activation key is limited to only about a quarter turn of the jackscrew (that is, the key can only be pushed from the front of the patient's mouth through about ninety degrees towards the patient's throat) For further turning of the jackscrew, the key has to be removed and reinserted into an adjacent jackscrew hole and the key has to be pushed through the same front-to-rear, ninety degree arc. At least partly because the activation key is restricted to such limited rotational movement, present jackscrew assemblies are constructed so that a quarter rotation of the jackscrew is ordinarily all that is required for any single incremental palate widening step.
Notwithstanding the universal use of such expansion screw assemblies for the construction of palate expander apparatus by orthodontists, this type of expansion screw is difficult to use. To fully understand this difficulty, it is necessary to appreciate that the jackscrews used in expansion screw assemblies are very small. Typically, the jack screws are no longer than about 11 or 12 millimeters and the diameter of the central region of the jackscrew, through which the holes for the activation key are formed is typically only about 3 millimeters, the holes being only about 1 millimeter in diameter. The activation key itself is only about 20-25 millimeters in length. Thus, with the palate expander positioned across a patient's palate and arched along the palate, the insertion of the tip of the small key into the obscure, small keyhole in the jackscrew is very difficult. Moreover, once the key is in the jackscrew keyhole, the key must be pushed fully to the rear of the patient's mouth to properly expose the adjacent jackscrew keyhole for the subsequent key engagement. In pushing the small key toward the patient's throat and in then pulling the key from the jackscrew keyhole, there is a risk of dropping the key down the patient's throat--a key accidentally dropped into a patient's throat and entering one of the patient's lungs constitutes a serious medical emergency. For this reason, one end of a string is ordinarily attached to the key, the other end being formed into a finger loop for the adjustor; nevertheless, several occasions of a key being dropped down a patient's throat have been reported.
A substantial problem associated with the above-described manner in which heretofore available expansion jackscrews are adjusted by a small wire key can be further understood by considering that the frequent adjustment--which may be as often as twice a day--of the palate expander jackscrew in a patient's mouth is necessarily performed by other than the installing orthodontist or his or her staff.
Considering that palate expander apparatus are ordinarily installed only in children between the ages of about six to fourteen years of age, the individuals responsible for the frequent actuation of the jackscrew are ordinarily the child's parents (or guardians). Although instructed in technique, usually by a dental technician, it is, for example, often difficult for patents to properly adjust the jackscrew by use of the wire key. There may be a fear of hurting the child and the child may be apprehensive and may not be a willing patient. Furthermore, a woman's long fingernails may increase the difficulty of holding and pushing the key, and a man may have difficulty in manipulating the small key, especially if he has large fingers and/or is unaccustomed to such relatively delicate and painstaking tasks. Still further, the child's mouth is usually small and has limited access with restricted visibility of the jackscrew to be actuated. Even further, the force required to push the key against the jackscrew's resistance to turning can cause the key to bend and pull out of the jackscrew and/or slip out of the operator's fingers. Such action can cause injury to the patient's mouth or the operator's fingers. Also, as above mentioned, at the extreme of travel, the key must be removed from the jackscrew keyhole very carefully so as not to be dropped down the patient's throat.
It can be appreciated that the orthodontist's initial adjustment of the jackscrew in the above-described manner to fit the palate expander to the patient's palate is made more difficult and potentially unsafe for both the patient and the orthodontist by the current AIDS situation. As a result of concern for both patient and doctor infection of the AIDS virus, most practitioners wear or are required to wear surgical gloves when working in a patients mouth, particularly if there is a possibility of any patient-doctor blood contact. The wearing of surgical gloves can make manipulation of the actuation key more difficult and thereby increase the risk of injury to the patient's mouth or the orthodontists fingers and resulting bleeding.
U.S. Pat. No. 3,800,420 to Gilbert Ouaknine discloses the use of a rack and pinion-type expansion screw assembly for use in palate expander apparatus and is addressed to certain potential problems associated with the use of a jackscrew-type of expansion screw. Nevertheless, such patent does not address the above-described problems that relate to the necessity of using a pin-type key to adjust the expansion screw. Consequently, so far as is known to the present inventor, the type of palate expander apparatus disclosed in the Ouaknine patent has never been commercialized.
For these and other reasons, practical improvements to presently available expansion screw devices are needed to make them easier and safer to use, and it is the intent of the present invention to provide such an improved expansion screw assembly and palate expansion apparatus for which adjustment of the expansion screw assembly can be easily performed with the fingers outside of the patient's mouth by the use of a conventional Allen wrench, screwdriver or the like.